1. Field of the Invention
The invention relates to a method of fabricating a semiconductor device.
2. Description of Related Art
Non-volatile memory is a type of memory that has been widely used inside personal computer systems and electron equipments. Data can be stored, read out or erased from the non-volatile memory countless number of times and any stored data is retained even after power supplying the devices is cut off.
In general, the typical non-volatile memory cell is designed to be comprised of a stacked gate structure including a floating gate and a control gate made of doped polysilicon. The floating gate is located between the control gate and a substrate in a floating state without connecting to other circuits, while the control gate is connected to a word line. Further, the non-volatile memory device also includes a tunneling dielectric layer disposed between the substrate and the floating gate, and an inter-gate dielectric layer disposed between the floating gate and the control gate.
Based on the design concept for improving the device integration, the sizes of the devices are reduced accordingly. In this case, an air gap ratio between the stacked gate structures (a ratio of a sectional area of the air gap to a sectional area of a space between the stacked structures) are usually increased to prevent resistor-capacitor delay (RC Delay) between the stacked gate structures, and floating gate coupling between the floating gates from increasing.
However, with the increasing degree of device integration, air gaps formed by using method of fabricating a non-volatile memory in prior art is relatively lower. As a result, the resistor-capacitor delay between the stacked gate structures and the floating gate coupling between the floating gates may not be effectively reduced.